This invention relates to a security system for a mobile medium such as an automobile or electric-powered car or train.
FIG. 1 shows an example of a conventional system of this kind applied to a vehicle. A steering mechanism 1 of the vehicle is provided with a lock mechanism 2. When the lock mechanism 2 is actuated, the steering wheel 1a can not rotate and so directional control of the vehicle is not possible. In the lock mechanism 2, when an electromagnet 5 is energized, a pin 6 is pulled out of a shaft hole 7 of a steering shaft 1b. The electric power is supplied to the lock mechanism 2 from a power source (not shown) via key switch 3 and a safety switch 4.
To start a vehicle having the thus-constructed mechanism, a key is inserted into the key switch 3 and is turned so as to turn on the key switch 3. In this state, the electromagnet 5 is not supplied with electricity and the steering wheel 1a is still in its locked state and cannot be rotated, since the safety switch 4 is still open. If, at this point, the safety switch 4 is pressed, the energizing circuit of the electromagnet 5 is activated so that the pin 6 is pulled out of the shaft hole 7, thereby enabling the steering mechanism 1 to operate. If, in this state, the engine is started, the vehicle is capable of being controlled directionally while on the move.
The thus-arranged conventional security system is defective in that, if the wires connected to the pair of terminals of the key switch are cut and thereafter the pair of terminals are directly connected to each other and the safety switch 4 is passed, the vehicle can be steered and made to move and, therefore, can be stolen easily. A complicated security switch arrangement can be applied in order to prevent the vehicle from being stolen. However, if the switch arrangement is complicated, the operation of releasing the lock becomes troublesome, resulting in a reduction of normal operating ease.